The invention is in the field of rock boring machines, and more specifically such machines for reaming substantially vertical holes, or holes at a slight angle from true vertical, by initiating rock boring at ground level and boring a predetermined distance underground. No known down reaming apparatus is capable of boring substantially larger holes (preferably having a diameter of at least four meters) in a substantially continuous manner.
U.S. Pat. No. 3,965,995 issued to Sugden discloses a machine for boring a large diameter blind hole in a sequential, non-continuous manner. The cutterwheel is mounted at the lower end of the machine for rotation about a horizontal tubular support. A gripper assembly secures the machine against the tunnel wall while thrust cylinders thrust the rotatable cutterhead downwardly. As the machine is advanced, the cutterwheel is rotated to make a first cut in the shape of the leading portion of the cutterwheel. The cutterwheel is then retracted out from the cut and is rotated about the axis of the hole. This repositions the cutterwheel so that when it is advanced again, during the next cutting step, it will make a second cut which crosses the first. This procedure is repeated until the desired cross-sectional configuration (e.g. circular) of the hole is obtained. The above described sequential boring method employing a gripper assembly and thrust cylinders has been found to be time consuming and requires a complex and expensive machine. U.S. Pat. No. 3,965,995 lists numerous prior art shaft forming machines, the disclosures of which are incorporated herein by reference.
U.S. Pat. No. 4,270,618 issued to Owens teaches an earth boring apparatus which is used for boring a blind pilot hole of a relatively small diameter which is subsequently enlarged by raise boring. Initially, the earth boring apparatus is employed to bore a blind pilot hole. Then the apparatus is removed from the hole and a room is blasted at the blind end of the hole. Next, the pilot hole cutterhead is replaced by a reamer and the apparatus is again inserted into the hole. The reamer is an adjustable diameter type and its diameter is increased once it is within the blasted room. The diameter of the reamer is increased by a plurality of cutter carrying arms which swing outwardly from the axis of rotation of the reamer. The earth boring apparatus is then raised from the room upwardly towards the ground surface to bore a hole of the desired diameter.
Similarly, U.S. Pat. No. 4,646,853 issued to Sugden et al. discloses a shaft boring machine having step-wise operation. The machine includes a cutterwheel assembly having a substantially horizontal axis of rotation and having multiple peripherally mounted roller cutter units. Motors are provided for rotating the cutterwheel assembly about its horizontal axis. A cutterwheel carriage and vertical guide columns support the cutterwheel assembly and allow movement of the cutterwheel assembly in a vertical plane. A base frame supports the vertical guide columns. The base frame is slewed in a substantially horizontal plane by a slew drive system. Plunge cylinders mounted on the cutterwheel carriage and the base frame lower and raise the cutterwheel assembly in a vertical plane. A lower gripper ring stabilizes the machine in the shaft and includes a circular track for supporting the base frame and further includes a lower gripper cylinder system for holding the gripper ring stationary in the shaft. An upper gripper ring provides further stabilization of the machine in the shaft and includes an upper gripper cylinder system for holding the upper gripper ring stationary in the shaft. Walking cylinders are mounted on the lower and upper gripper rings for raising and lowering the rings. U.S. Pat. No. 4,646,853 discloses additional prior art patents pertaining to shaft boring machines, the disclosures of which are incorporated herein by reference.
U.S Pat. No. 4,270,618 issued to Owens cites prior art patents for drilling machines located at an upper level which bore a large diameter hole in a single downward pass, drilling machines at an upper level which first drill a small pilot hole on a single downward pass and then enlarge the pilot hole in a single upward pass, and machines having expandable reamers. These prior art patents are incorporated herein by reference.
U.S. Pat. No. 3,840,272 issued to Crane et al.; U.S. Pat. No. 3,999,616 issued to Crane et al.; U.S. Pat. No. 4,009,909 issued to Robbins et al.; and patents cited therein disclose machines for upward tunneling, as opposed to down reaming.
A need thus exists for a down reaming apparatus capable of boring a large diameter hole in a substantially continuous manner.
A need also exists for this type of down reaming apparatus which is stabilized in the bored shaft by means of non-gripping stabilizer assemblies having rotatable elements which allow vertical movement of the down reaming apparatus within the tunnel.
A need also exists for this type of down reaming apparatus in which a gear assembly is employed to multiply the torque transmitted from the drill string to the cutterhead.
A need also exists for this type of down reaming apparatus in which a weight assembly is secured on the frame of the down reaming apparatus such that loads from rotation of the cutterhead are transmitted through the frame and into the weight assembly.
A need also exists for this type of down reaming apparatus in which the weight stack has a manway therethrough for access by workers to the cutterhead for cutterhead repair and/or reconfiguration.
A need also exists for this type of down reaming apparatus of this type in which the cutterhead diameter can be increased by the addition of a single spacer having a cutter assembly thereon.